JavaScript: The Definitive Guide, Fourth Edition

Name

Math.log( ) — compute a natural logarithm

Availability

JavaScript 1.0; JScript 1.0; ECMAScript v1

Synopsis

Math.log(x)

Arguments

x

Any numeric value or expression greater than zero.

Returns

The natural logarithm of x.

Description

Math.log( ) computes log₃x the natural logarithm of its argument. The argument must be greater than zero.

You can compute the base-10 and base-2 logarithms of a number with these formulas:

log₁₀x = log₁₀e·log_ex

log₂x = log₂e·log_ex

These formulas translate into the following JavaScript functions:

function log10(x) { return Math.LOG10E * Math.log(x); }
function log2(x) { return  Math.LOG2E * Math.log(x); }